GSMArena did the battery tests on quite a few comparable smartphones recently, culminating with the Galaxy Nexus on 30/12/2011. I refer below the most likeable five [5], which were under consideration while many of us were on the N9 foray. It's amazing to see that our beloved MeeGo-Harmattan fared much better than the other [most] expected ones.

3G Talk Time:
How the battery went from 100% to 0% on talk time over a 3G network.

Web Browsing:
How a fully charged battery took time, while refreshing web pages with their automated script, to deplete its juice.

Video Playback:
How the smartphone/s used 90% of their battery (the trial ends there) after continuous video playback.

Overall Score:
They conclude with the most important of their tests, the "overall usage". That number [in red] means that you will have to charge that smartphone every that many hours if you do one [1] hour each of browsing, video playback and 3G calls per day.

CONCLUSION:
Apple iPhone 4S works out to be the overall leader with 45 hrs. of Endurance Rating, while doing fairly well under most individual tests, sure some others beat it irregularly... however, our own Nokia N9 doesn't seem to much lag behind - scoring 39 hrs. of endurance, beat only by the SGSII at 40 hrs... which is incognito to me. While the Galaxy Nexus sure was a disaster at 35 hrs. faring nothing scholarly at the individual tests as well. Quite drab I'd say [though non-technically!]... while even our 'twin-sister' with WP7.5 Mango under the same shell fared better !

But, man-o-man!Did the Nokia N9 rock?
Second best [keeping the SGSII at par]! That sounds good... what with all the talk about 'idle consumption', 'older processor', 'poor battery life' and the likes? GSMArena suggests that reasonably heavy users should expect to get about a day and a half from their N9s. Good enough?

Qorax

Ps.: I'm a non-techie... do not know the wherewithals... but my overall experience with my N9, since around a month, has been astounding, vis-a-vis my iPhone4. And GSMArena seems to echo that!

Fifteen Tips for extending the Nokia N9 battery life(Ok, for any smartphone actually!)

Our devices today are genuinely doing more... and due to our usage patterns - they are working overtime, seriously! Thus, our phone just can't keep pace with its battery. Unless their power-packs go nuclear [it'd then cost a bomb!] we remain stuck with abysmal battery life, even for the best of them.

If we don't we use them sparingly, disable most functions, switch-it-off regularly, slow down the GSM, use a corded headset etc. - they'd be dead by evening, if not by mid-day. But hey, we are in the smartphone era, aren't we? How dumb it'd be to switch-off over 50% of their functions? We sure need our steady workload of running apps, browsing the Web, sending e-mail, clicking snaps etc. (yeah, making calls too!).

Well, most smartphone batteries today are rated at around 5 watt-hours, meaning that they can deliver a constant charge of 1W to the device over a period of 5 hrs. Thus, if our phone 'actually' uses 1W per hour, and we remove the charger at 7:00 am, we can expect it to be dead by lunchtime. Which, we definitely don't want. Thus, the key to increasing our phone's battery life is to reduce the amount of power the handset uses per hour. Here's what we could/should do:

1. Power Saver Mode:
This is the first task. Our phones have a built-in power-save mode, which by default usually turns on when the battery level drops to 20%. However, we can set it to kick-in at 30% instead. And the sooner the phone switches to Power Saver mode, the longer its battery will last.

2. Bluetooth & Wi-Fi:
These two are serious battery drainers. The extra radios are constantly listening for signals. By turning them off, when we are not using them, we could actually add around 1 to 2 hrs. more to our phone's battery life.

3. The GPS:
A big battery sucker... the phone's GPS unit is used by various apps to provide services ranging from finding nearby restaurants to checking us in on social networks. We can revoke these apps' access to our phone's GPS. Also, when we install them, many apps will ask our permission to use our location... for most of them we could say No (if a game, screensaver, or wallpaper app asks for the location, we should definitely be suspicious - 'coz they don't need that data).

4. Talk Vs E-mail:
Cellular data connections use between 2-4 times as much battery power as voice connections. For simple communications, call and leave a message instead of e-mailing. Turning-off push email or reducing the frequency of email updates increases our battery power by 50%.

5. Social Networking Apps:
Yes, we need them... but their non-essential notifications also drain our battery severely. It seems every app now constantly searches the internet for updates, news, messages etc. which consume energy. However, do we need to be instantly alerted always'? Turning-off superfluous notifications will help our battery last substantially longer.

6. Screen brightness:
We love the large, colorful display, but it's the battery's mortal enemy. More than anything else in the phone, the display consumes battery at a severe pace. Most phones include an auto-brightness feature that automatically adjusts the screen's brightness to suit ambient lighting levels. However, we'll get even better results by turning the screen's brightness down to the lowest tolerable setting.

7. Screen Timeout:
This setting controls how long our phone's screen stays lit after receiving an input, say a tap. Every second counts here, so we should set our timeout to the shortest available time. If our screen timeout is currently set to 2 minutes, consider reducing that figure to 30 seconds or less. Saves a lot of energy.

8. Ringtone Control:
We might not be fully aware, but turning down the volume of our ringtones a few notches, saves a lot of juice... the same goes for message tones.

9. Vibration Vs. Ringtone:
We need it. But unfortunately, vibrating uses much more power than playing a ringtone. After all, a ringtone has to only make a tiny speaker-membrane vibrate. In contrast, the vibration motor swings to make our whole phone shake - and that consumes a lot more power. If we don't want to be disturbed audibly, consider zeroing the volume and leave the phone in view - so we can 'see' a new call. This approach is as courteous to the battery as it is to our friends, colleagues & neighbors.

10. Multitasking:
Multitasking, the ability to run more than one app at a time, is a powerful smartphone feature. It also burns a lot of energy, because every app we run uses a share of our phone's processor cycles. By killing apps that we aren't actually using [viz. music player, games, browsers etc.] from the background, we can heftily reduce our CPU's workload and cut down its power consumption.

11. Update the OS:
One of the biggest battery drainer is also our operating system. Manufacturers/vendors tend to improve power consumption from version to version, besides doling fixes, bugs & tweaks. So, we should update our phones whenever we can.

12. Keep it cool:
Lithium Poly Ion (Li-Poly or Li-Ion) batteries have allowed for up to 40% more battery capacity than previous batteries of the same size. However, while that means more talk-time, we also need to keep them at optimum temperature (usually around room temperature) and away from hot environs. Which, if not draining the battery, surely diminishes the battery's ability to hold charge.

13. Carry a spare:
If we regularly push the limits of our smartphone, it'd be wise to buy a spare battery and carry wherever. Usually a battery typically cost $10-30, depending on the phone. However, this isn't a choice for iPhone & Nokia N9. Which is why [see below]...

14. Carry a Portable Battery Life Extender:
E.g.: http://www.buybits.com/Product/8938/...-sku-8938.aspx
These are External Battery Packs (very handy), connects to our phone via an USB cable [compatible phone required, the Nokia N9 is one such] extending our phone's battery life by up to four [4] times. There are lots of variants around... e.g. the Medis 24-7 Power Pack ($40) uses fuel-cell technology to recharge the phone battery, while Solio offers solar-powered rechargers ($80-170). There are also more traditional battery life extenders, such as Turbo Charge, ($10-20) which uses plain AA batteries.

15. Charge the smartphone whenever possible:Contrary to general opinion - this is perfectly OK, even desirable! With the old nickel-cadmium (Ni-Cad) batteries, the advice was to let them run down completely and then fully recharge. That's not the case with today's lithium ion (Li-Ion) batteries, which are in all smartphones... even the user manuals are often wrong. Feel free to "Top Up" today's smartphones anytime - look for outlets in meeting rooms, airports or charge while driving. There will be many more charge cycles possible to our batteries if we recharge from 40% (used capacity), than from 80%.

CONCLUSION

These days, we use our phones for many activities - making it all the more catastrophic when our devices run out of charge. The problem is, while smartphone capabilities have increased dramatically in recent years, their battery technology haven't kept pace. Everybody seem to have this problem... we keep cribbing that our smartphones just don't last long enough.

However, there are many things we can do to significantly increase the time between charges... it's a lot of little things that help. There are plenty more tips and tricks to prolonging our battery life, however the aforesaid 15 could be the very basis to nearly double-up our smartphone usage time.

Another battery drainer that can be switched off is 3G.
You don't need 3G for calling and you most probably don't need 3G for regular web surfing. 2.5 G is usually sufficient unless you're streaming videos or downloading files.

Yeah read all that before, but good to see it all summarized, so thanks!
I think we'll see substantial improvements WRT battery usage/consumption in 1.2.
(they were mostly supposed to be addressed with 1.1, but quite a few nasty bugs were missed)
There's def. areas it could do much better in, even if it is one of the best "overall".
I was disappointed w/the 3G consumption rate, web browsing consumption's pretty poor too.

15. Charge the smartphone whenever possible:[/SIZE][/FONT]Contrary to general opinion - this is perfectly OK, even desirable! With the old nickel-cadmium (Ni-Cad) batteries, the advice was to let them run down completely and then fully recharge. That's not the case with today's lithium ion (Li-Ion) batteries, which are in all smartphones... even the user manuals are often wrong. Feel free to "Top Up" today's smartphones anytime - look for outlets in meeting rooms, airports or charge while driving. There will be many more charge cycles possible to our batteries if we recharge from 40% (used capacity), than from 80%.

Any source on this one? Not like I have a source that disproves it but definitely counter to what I have been reading on all battery-saver advises. Thanks.

15. Charge the smartphone whenever possible:Contrary to general opinion - this is perfectly OK, even desirable! ...That's not the case with today's lithium ion (Li-Ion) batteries... Feel free to "Top Up" today's smartphones anytime ...There will be many more charge cycles possible to our batteries if we recharge from 40% (used capacity), than from 80%.

Any source on this one? Not like I have a source that disproves it but definitely counter to what I have been reading on all battery-saver advises. Thanks.